My first two tbh I built had solid bottoms. I have since sold them. Then I built two with a screened bottom but with a hinged bottom board that I could open for ventilation. Never opened them, until 1 died out, then I open it and tore off the screen to clean it out. The next two I built I just hinged the bottom board with no screen. To clean, I just swing down the bottom board and scrape with a paint scraper. I did build screened add-ons that I can attach with the bottom board swung open, that have slots for inserting a tacky board for mite drop counts, but have never used them. To sum all of this up, I like the hinged solid bottom board the best. I have not needed screens in the three years I have had them.